1. Field of the Invention
The present invention relates to a power module such as a transfer-mold type IPM (Intelligent Power Module).
2. Description of the Background Art
In a power module used for an inverter, with a conventional configuration in which an IGBT (Insulated Gate Bipolar Transistor) and an FWD (Free Wheeling Diode) are connected in parallel with each other, it is difficult to reduce losses in the low current range due to the characteristics of the IGBT.
To improve losses in the low current range, it is considered to use a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) instead of an IGBT. However, with the MOSFET, there is a problem that the allowable current decreases, since the on-voltage in the high temperature/high current range increases.
To solve such problem, there is considered a configuration in which an IGBT with a low saturation voltage in the large current range is connected in parallel with a MOSFET with a low saturation voltage in the small current range (see, for example, Japanese Patent Application Laid-Open No. 04-354156 (1992)).
However, the configuration described in Japanese Patent Application Laid-Open No. 04-354156 (1992) is lacking in the viewpoint of adjustment of loss sharing between the IGBT and the MOSFET. Hence, there is a problem that the cost-performance of a power module cannot be optimized by the above-described adjustment.